Hubble Sees Bare Neutron Star Streaking Across Space

November 9, 2000: It's as big as Manhattan Island, is 10 trillion times denser than steel, and is
hurtling our way at speeds over 100 times faster than a supersonic jet. An alien
spaceship? No, it's a runaway neutron star, called RX J185635-3754, forged in
a stellar explosion that was visible to our ancestors in 1 million B.C. Precise
observations made with the Hubble telescope confirm that the interstellar interloper
is the closest neutron star ever seen. The object also doesn't have a companion
star that would affect its appearance. Now located 200 light-years away in the
southern constellation Corona Australis, it will swing by Earth at a safe distance
of 170 light-years in about 300,000 years.

Q & A: Understanding the Discovery

1.
Why is the neutron star's closeness to Earth and lack of a companion so important to astronomers?

A neutron star is the dense, compact corpse of a massive star that died in a violent explosion. Because this object is the closest and brightest of the few known isolated neutron stars, astronomers can easily study it and use information about its size, brightness, and age to test theories about a massive star's life and death.

2.
How fast is the neutron star traveling?

This runaway object is one of the fastest moving stars in the sky, traveling at a speed of about 240,000 miles an hour (389,000 kilometers an hour).